The invention relates to a local communication bus system comprising a serial control bus attached to a plurality of devices, that are furthermore pairwise interconnected by respective signal interconnections and include at least one plural-interconnected switchbox means, said system being able to establish a signal path between an initiating or source station and a destination station.
A single-channel control bus has been described in U.S. Pat. No. 4,429,384, herein incorporated by reference. Such a communication bus is particularly suited for transfer of control signals between various devices for consumer entertainment, devices for executing household chores, and devices for producing various maintenance and management control signals in a domestic environment. A different kind of serial bus has been disclosed in U.S. Pat. No. 4,689,740. This particular serial bus has separate clock and data wires. A still different set-up is a single data wire, a single clock wire, and a single word enable wire. A still different set-up is a single data wire, a single bit synchronization wire, and a single word synchronization wire. Serial in this context means that the information transmitted is represented by at most two wire signals, any other wire being exclusively used for controlling and/or synchronizing the transfer.
For simplicity, only the system according to the first referenced type is considered hereinafter. In addition to the control bus, the various devices are pairwise interconnected by signal interconnections. Herein, pairwise means that either exactly two devices are interconnected, or that one particular device operates as signal source, whereas the others function exclusively as signal destinations. An example would be one audio amplifier that can selectively power either one of two (or more) loudspeaker boxes. The signals may be analog or digital and may relate to audio video, or other information. Certain devices, although attached to the control bus, need not be interconnected to such signal interconnection inasmuch as they have little or no signal handling facilities, such as switches, sensors et cetera. For these devices, the control bus would provide a data path of sufficient transport capability. Particular properties of such system are the low level of data processing facilities of many of the interconnected devices, and also the frequent configuration changes encountered inasmuch as many devices are portable and liable to plugging and unplugging in various physical attachment points of the control bus. In typical circumstances, such control bus could be wired to all rooms of a house or appartment and in each wired room have one or more wall-mounted plugs. Of course simpler configurations would also do. The devices often have only a single signal interconnection; anyway, the switchbox means have at least two such signal interconnections, typical values are four to six.